In this work we investigate the catalytic activity of PtRu electrodeposits of distinct atomic composition towards methanol oxidation as a function of the "aging" of the electrodes. Electrochemical results show that those compositions containing more Ru present a peak of activity during the aging, whilst Pt-rich deposits present a continuous deactivation. Results are interpreted in terms of a progressive deactivation of Ru sites, which emulates a continuous change in the atomic composition. The maxima observed for the electrodeposits correspond to the time needed to attain compositions located in the range of good activity for methanol oxidation. (C) 2010 Elsevier B.V. All rights reserved.